The invention relates to the field of tool manufacturing and remanufacturing and, in particular, to a fixture apparatus for holding and manipulating a workpiece and a system utilizing the same.
The use of cutting tools having replaceable cutting inserts began as long ago as 1917, when Fred P. Lovejoy invented the use of replaceable blades in order to obtain the economic advantages of having to replace the dull portion of the tool not the whole tool itself.
The next major improvement in this process was the invention of the tungsten titanium carbide insert by Philip M. McKenna in 1938, especially for use in milling machines. A typical milling machine is an apparatus that features a rotating mill head having a number of indexable cutting inserts, where the rotating head is passed over the workpiece to remove material from the workpiece.
Since the time of the invention of the carbide cutting insert, tremendous effort has been made to understand the myriad factors affecting the performance of cutting inserts. These factors include insert geometry, insert construction, temperature, cutting forces, workpiece material characteristics, and chip control. In fact, Kennametal, Inc. founded by Philip McKenna, lists thousands of insert geometry, size, composition, and coating combinations in order to meet the requirements of differing applications. Despite the overwhelming number of inserts that are available, standard inserts are still xe2x80x9cstandardizedxe2x80x9d.
Inserts can be manufactured in various ways. The most common basic materials are tungsten carbide or tungsten titanium carbide combined with a metallic binder such as cobalt. It is also possible to construct inserts from ceramic material. These are referred to as Cermet. Various thin film coatings can be applied to the surface of the cutting insert. Examples of common thin film coatings are titanium nitride, aluminum oxide, chromium nitride, titanium carbo-nitride, titanium aluminum nitride and diamond. Coatings are used to improve the performance and durability of the insert. Each material/coating combination has a particular application to which it is most suited.
In addition to material choices, various basic geometric shapes can also be selected. The most common are the square, triangle, diamond rhomboid, rectangle, hexagon and round. Added to this complexity is a choice of fifteen different clamping options, five different cutting edge forms, dimension tolerance classification, insert thickness, etc,.
Some inserts have only one sharpened edge suitable for cutting. However, most indexable inserts have a plurality of cutting edges. Once a particular cutting edge has become dull, the insert is indexed in its holder to expose a new cutting edge. Until recently, it was widely held that an insert was useless once all of its cutting edges had been dulled. Accordingly, dulled inserts were typically discarded as scrap. The growing acceptance of remanufactured inserts has disproved the belief that dulled inserts are valuable only as scrap. In fact, inserts remanufactured using the present inventor""s remanufacturing methods, disclosed and claimed in U.S. Pat. No. 5,957,755 and incorporated herein by reference, have found acceptance in industries, such as aerospace, automotive, toolmaking and heavy equipment, that had heretofore utilized only new cutting inserts. By remanufacturing their cutting inserts, companies have been able to customize their tools to achieve enhanced performance in their particular application, while realizing a significant cost saving on a per edge basis.
The remanufacturing process has typically involved clamping an insert into a single insert holder, sharpening one edge of the insert, unclamping and indexing the insert, and repeating this process until all edges of the insert are sharpened. Once the insert is completed, the insert is removed and another dull insert is completely sharpened. This process is advantageous for remanufacturing inserts in small quantities, as the time required for set-up is relatively low. However, the continuous unclamping and indexing required by this process is too time consuming to be cost effective when remanufacturing large quantities of the same insert. Given the widespread acceptance of remanufactured inserts, and corresponding increase in demand for these inserts, there is a need for a way to increase the volumes of inserts that are remanufactured.
In addition to the need for increased throughput of remanufactured inserts, experience has shown that certain geometries, such as the helical bias grinds disclosed in the inventor""s U.S. Pat. Nos. 5,957,755 and 6,171,031, which is also incorporated herein by reference, are difficult, if not impossible, to mold into new inserts. Further, it has been found that users of ground inserts can achieve superior performance over new molded inserts due to the ability to achieve a keener edge and to inexpensively adjust top rakes to optimize the edge for a particular application.
One way to realize an increase in remanufacturing throughput and provide the advantages of a ground edge to both remanufactured and new inserts, is to purchase and operate sophisticated computer numerically controlled (CNC) grinding equipment. However, such a solution requires a significant capital investment in purchasing the necessary equipment. In addition, this equipment requires the retention of qualified programmers and operators, who are not found in abundance and, once found, must be paid relatively high salaries. This solution may be acceptable to large-scale manufacturers of new inserts but is generally not financially feasible for smaller scale manufacturers. Further, in order to maintain a cost advantage over new inserts, any machine for increasing remanufacturing throughput must be made at relatively low cost and must be operable by non-technical personnel.
A number of United States Patents address the problem of fixturing. However, each has significant drawbacks that make them unsuited to solve the present problem. For example, U.S. Pat. No. 5,226,637, titled xe2x80x9cCLAMPING DEVICExe2x80x9d, discloses a clamping fixture utilizing a driving mechanism for driving an input member toward the clamp main body, and a wedge type converting mechanism for converting a driving force supplied to the input member from the driving mechanism into a clamping force against the workpiece.
This clamping device is effective in some applications, but is ineffective at securely clamping inserts on a high volume basis. First, this clamping device uses a manually actuated clamping screw as the driving mechanism, requiring too much time for clamping, unclamping, and indexing. Further, the movable jaw is driven in a single direction to force the workpiece against a fixed jaw. This unidirectional clamping allows the workpiece to move upward between the jaws, preventing the workpiece from being positively seated and, consequently, from being ground to the exacting tolerances required for a remanufactured cutting insert to be effective. Finally, it is not adapted to clamp a variety of workpieces and, therefore, is of limited usefulness in remanufacturing.
Another fixture is disclosed in U.S. Pat. No. 5,056,766, titled xe2x80x9cPRECISION MACHINE VICExe2x80x9d. This patent describes a fixture that employs a fixed jaw and a moveable jaw and employs a series of notches in the base as a guide means to stabilize clamping. A pin engages, at its lower end, a guide with opposite flanges. The guide also has a central wedge with an arcuate load-bearing surface. The pin extends through a rotatable clamp disposed through an angling shoulder on the moveable jaw and into a chamber in the base for engagement with the guide means to insure precise positioning. Tightening the pin into the guide snugs the upper surface of the wedge, flange, or both, into engagement with the upper surface of the chamber of the base, causing the moveable jaw to move toward the stationary jaw.
As was the case with the patent described above, this device also uses a manually operable clamping screw and therefore requires excessive time to unclamp and index. In addition, this vice also produces a unidirectional clamping force that prevents positive positioning between the jaws. Accordingly, this vice is also ineffective at securely clamping inserts on a high volume basis.
Another fixture is described in U.S. Pat. No. 5,718,420, titled xe2x80x9cWORKHOLDING WEDGE CLAMPxe2x80x9d. This patent discloses a device that uses a wedge actuator to move a slidable jaw. As with the previously mentioned patents the wedge is driven by a clamping screw and exerts a unidirectional clamping force on the workpiece. Accordingly, this fixture is also ineffective at securely clamping inserts on a high volume basis.
U.S. Pat. No. 4,958,818, titled xe2x80x9cCLAMPING BLOCKxe2x80x9d, discloses a holder for use in partial machining tasks, or as a clamping means for exchangeable tools. This device is a variation of what is commonly referred to as a toe clamp and employs a fixed jaw and a movable jaw that is driven toward the fixed jaw via a drive screw. The top portion of the movable jaw has a number of teeth that contact the workpiece, and the movable jaw and stationary jaw have mating details along the base portion that prevent upward movement of the movable jaw once the workpiece is clamped.
As was the case with the other patents described herein, the clamping block of this patent has drawbacks that make it ill-suited for the present application. First, the use of a manual drive screw is time consuming. Second, lack of clearance between the bottom of the movable jaw and the base plate means that the teeth of the fixed jaws are adapted to provide a unidirectional clamping force upon the workpiece. Finally, the mating details required to prevent the upward movement of the movable jaw make this block prone to fouling by debris generated during the grinding process. This debris prevents positive locking of the clamp block and, therefore, the block requires frequent cleaning.
A fixture for remanufacturing cutting inserts that increases throughput, requires a relatively low up-front cost, is operable by non-technical personnel, reduces the overall time required for unclamping and indexing inserts, is effective at clamping inserts on a high volume basis, may be used for a wide variety of inserts, provides positive seating of an insert, allows the insert to be ground to exacting tolerances, and does not easily fill with debris, is not known in the art.
The present invention is a fixture apparatus for securing at least one cutting insert. In its most basic form, the apparatus includes a base plate having a top surface. A clamp block extends from the base plate and has a clamp surface disposed at a first angle from the top surface of the base plate. A locator block extends from the base plate and includes a locator surface disposed opposite the clamp surface of the clamp block. An alignment means is also provided for aligning the cutting insert relative to the locator surface of the locator block. A clamp wedge is disposed between the clamp surface of the clamp block and the locator surface of the locator block. The clamp wedge includes a top, a bottom, a drive shaft extending from the bottom and through the base plate, a bearing surface disposed against the clamp surface of the clamp block and in substantially parallel relation to the clamping shaft, and a wedge surface disposed at a second angle relative to the bearing surface. The second angle of the wedge surface is complimentary to the first angle of the clamp surface of the clamp block such that the wedge surface is disposed in substantially parallel relation to the locator surface of the locator block. Finally, a drive means is provided for extending and retracting the clamp wedge.
In operation, the clamp wedge is extended by the drive means. The cutting insert is then disposed against the locator surface of the locator block and aligned relative to the locator surface by the alignment means. The clamp wedge is then retracted such that the wedge surface of the clamp wedge securely holds the cutting insert in a predetermined location against the locator surface.
In the preferred embodiment of the present invention, the bottom surface of the base plate has an angled front portion to accommodate a pneumatic cylinder, which is the preferred drive means. This angled front is preferably perpendicular to the top of the pneumatic cylinder and is disposed at a complimentary angle relative to the clamp surface of the clamp block such that the clamping shaft is driven in substantially parallel relation to the clamp surface.
The preferred base plate is wider at its front than its rear and includes a pair of side walls that each form an eight degree (8xc2x0) angle from a plane formed by the centerline of the base plate. This arrangement is preferred as it allows multiple fixture apparati to be mounted to a rotary table. In other embodiments, however, base plates having substantially parallel sidewalls to allow multiple apparati to be mounted in a straight line arrangement.
The preferred base plate also includes an attachment means for attaching the base plate with an angle adjustment means, such as a sine base, riser block or incline table, that allows the rake angle of the insert to be varied. In the preferred embodiment, each base plate is attached to a single standard twelve inch sine base, which allows the rake angle of the insert to be varied between about minus fifteen degrees (xe2x88x9215xc2x0) and about twenty-five degrees (25xc2x0).
In the preferred apparatus, the clamp block and locator block are removably attached to the base plate in order to allow individual blocks to be replaced in the event that they are inadvertently damaged. However, in other embodiments the clamp block and locator block may be formed integral to the base plate. The preferred clamp block includes a pair of clamp rails that includes a pair of clamping surfaces that extend at an angle of approximately ten degrees (10xc2x0) from the top surface of the base plate. However, in other embodiments, the clamping surface may extend from about one degree (1xc2x0) to about forty-five degrees (45xc2x0) from the top surface of the base plate.
In the preferred embodiment, a stop assembly is attached to the clamp block for stopping the upward travel of the clamp wedge. The stop assembly is preferably adjustable such that the distance between the wedge surface of the clamp wedge and the alignment means is small enough to prevent inserts from inadvertently falling between the clamp wedge and the alignment means. This distance is approximately 0.030 inches in the preferred embodiment. The preferred stop assembly is a screw and locknut mounted within a notch in the top of the clamp rail of the clamp block.
The preferred locator block is disposed perpendicular to the base plate. In this embodiment, the alignment means includes a locator blade and a locator pin removably attached to, and extending from, the locator surface. The preferred locator blade has a thickness of approximately 0.110 inches thick and has a top surface that is segmented into two sections. The first section being substantially flat and the second being sloped downward at an angle of approximately twenty-five degrees (25xc2x0) relative to the horizontal plane. The preferred locator pin is a round pin having a cap that includes a flat portion along its edge and an angled portion disposed at a twenty degree (20xc2x0) angle to its shaft.
The preferred clamp wedge includes a wedge surface that is angled at ten degrees (10xc2x0) to correspond with the ten degree (10xc2x0) angle of the preferred clamping surface of the preferred clamp block. The preferred clamp wedge includes a threaded round drive shaft that is removably attached to the clamp wedge at one end and to a pneumatic cylinder, which is the preferred drive means, at the other.
The preferred apparatus also includes a cover assembly for covering the drive components such that they are protected from debris created during the remanufacturing process.
In its most basic form, the remanufacturing system of the present invention includes a grinding wheel and a horizontal grinding table. A fixture apparatus, as described above, is secured to the grinding table relative to the grinding wheel. A control means is in communication with the drive means of the fixture apparatus such that the drive means is caused to actuate the clamp wedge of the fixture at a desired time. In the preferred system, the control means is a pneumatic control that is in communication with pneumatic cylinders attached to a plurality of apparati. However, in other embodiments, such as those in which hydraulic or electromechanical drive means are utilized, other art recognized controls are provided.
Therefore, it is an aspect of the invention to provide a fixture for remanufacturing cutting inserts, and for manufacturing new cutting inserts with a ground edge, that increases throughput.
It is a further aspect of the invention to provide a fixture for remanufacturing cutting inserts, and for manufacturing new cutting inserts with a ground edge, that involves a relatively low up-front cost.
It is a further aspect of the invention to provide a fixture for remanufacturing cutting inserts, and for manufacturing new cutting inserts with a ground edge, that is operable by non-technical personnel.
It is a further aspect of the invention to provide a fixture for remanufacturing cutting inserts, and for manufacturing new cutting inserts with a ground edge, that reduces the overall time required for unclamping and indexing inserts.
It is a further aspect of the invention to provide a fixture for remanufacturing cutting inserts, and for manufacturing new cutting inserts with a ground edge, that is effective at clamping inserts on a high volume basis.
It is a further aspect of the invention to provide a fixture for remanufacturing cutting inserts, and for manufacturing new cutting inserts with a ground edge, that provides positive seating of an insert.
It is a further aspect of the invention to provide a fixture for remanufacturing cutting inserts, and for manufacturing new cutting inserts with a ground edge, that allows the insert to be ground to exacting tolerances.
It is a still further aspect of the invention to provide a fixture for remanufacturing cutting inserts, and for manufacturing new cutting inserts with a ground edge, that does not easily fill with debris.
These aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims and accompanying drawings.